The present invention relates to a method and apparatus for lifeline call redirection in a voice over digital subscriber line system, and a system incorporating the same.
Digital Subscriber Line (DSL) modem technology has enabled the transmission of digital information at duplex rates from 144 Kbits/s to over 1 Mbits/s over the subscriber loop. The demand for additional telephone lines and integrated telephony and data services has given rise to Voice over DSL (VoDSL) solutions. For example a VoDSL system may provide 4 voice channels carried within the digital data over a single twisted pair subscriber loop from a Line Terminating Equipment (LTE) located in the Central Office to a Customer Premises Equipment (CPE). In one implementation a VoDSL system carries the voice channel(s) in band as encoded data within the data stream and therefore there is no baseband POTS (Plain Old Telephony Service) as would be the case with for example ADSL or G.Lite. Unlike normal telephony the derived voice method of VoDSL requires local power at the CPE to perform the modulation and demodulation.
Conventional analogue POTS telephony over a twisted pair to the LTE has the benefit that during power failure at the customer premises emergency calls can still be placed since the line and the handset at the customer premises are powered from the central office. A disadvantage of existing VoDSL modems is that the amount of power required for normal operation could severely limit the operational loop length if power is fed from the central office and not provide a service able to reach the majority of consumers. This has limited deployment of VoDSL systems to subscribers having an additional conventional POTS line which can be used in the event of power failure. Absence of support for lifeline services has therefore severely hindered deployment into the small business and especially the residential market.
In a voice over DSL system where a number of derived telephone ports are supported, in-band, over a single physical copper pair, it may be required to provide a xe2x80x9clifelinexe2x80x9d service. This is a condition to which the system reverts in the case of CPE power failure, modem failure etc. consequently, this would then provide normal telephony service and in particular access to emergency services. Under such conditions it may only be feasible to support a single xe2x80x9clifelinexe2x80x9d telephone port on the CPE modem (due to power feed constraints, battery provision etc). This would therefore result in a number of the derived telephone ports being unavailable for service.
Reference is here directed to our co-pending application Ser. No. 09/305,943 which relates to a filter arrangement for a telephone subscribers installation providing access to a plurality of telephone instruments.
The invention seeks to provide an improved method and apparatus for providing lifeline call support in a voice over digital subscriber loop system.
According to a first aspect of the invention, there is provided customer premises equipment arrangement for a telecommunications subscriber, the arrangement comprising a subscriber loop port; a plurality of switchable local subscriber ports; and a router circuit; wherein each of said plurality of local subscriber ports is switchably connectable in parallel to said subscriber loop port and wherein said router is arranged to monitor signals received at said subscriber loop port and to selectively disconnect at least one of said local subscriber ports responsive to said signals.
According to another aspect of the invention, there is provided customer premises equipment arrangement for a telecommunications subscriber and adapted to provide a lifeline voice service under a fault condition, the arrangement comprising a subscriber loop port whereby the arrangement is coupled to the subscriber loop; a plurality of switchable local subscriber ports each providing access to a respective telephone instrument; and a router circuit whereby, under normal conditions, voice calls may be routed each to a respective loop port; wherein each of said plurality of local subscriber ports is switchably connectable in parallel to said subscriber loop port and wherein said router is arranged to monitor signals received at said subscriber loop port and to selectively provide and maintain voice access to one said loop port under a said fault condition.
The invention is also directed to a method by which the described apparatus operates and including method steps for carrying out every function of the apparatus.
According to a further aspect of the invention, there is provided a method of operating a customer premises equipment arrangement comprising a subscriber loop port and a plurality of local subscriber ports selectively connectable to said subscriber loop port; the method comprising the steps of: receiving signal at said subscriber loop port indicative of a local port; and selectively coupling one of said local subscriber ports to said subscriber loop port responsive to said signal.
According to a further aspect of the invention, there is provided a method of operating a customer premises equipment arrangement comprising a subscriber loop port coupled with a subscriber loop to a line termination equipment and having a plurality of local subscriber ports each connectable to a telephone instrument so as to provide a voice over digital subscriber line service to each said telephone instrument, the method comprising routing incoming voice calls each to a respective local point determined from signalling associated with that call, and, under a fault condition in each customer premises equipment arrangement, routing an incoming voice call to a selected one of said local ports and inhibiting further incoming calls while that call is in progress.
The invention also provides for a system for the purposes of digital signal processing which comprises one or more instances of apparatus embodying the present invention, together with other additional apparatus.
The subscriber equipment described below operates, during power fail or modem failure at the CPE, so as to automatically map any incoming telephone calls to a CPE system to the designated xe2x80x9clifelinexe2x80x9d POTS xe2x80x98phone port. In this way, an external incoming call to any of the derived telephone ports at the CPE will be terminated at the designated xe2x80x9clifelinexe2x80x9d POTS port. It is assumed that the installation will be such that the xe2x80x9clifelinexe2x80x9d telephone (or telephones on extension) will be known and physically accessible by all users (such as a small office environment).
During xe2x80x9clifelinexe2x80x9d operation all external telephone calls to any of the logical ports on a given VoDSL CPE are terminated at the designated xe2x80x9clifelinexe2x80x9d telephone. Preferably, only one incoming call at once to a given VoDSL CPE is supported during xe2x80x9clifelinexe2x80x9d operation, others are treated by the LE as unavailable or engaged.
Automatic redirection of all in-band telephony channels to one xe2x80x9clifelinexe2x80x9d telephone port may be effected and blocking of incoming calls to non-lifeline logical telephony ports due to VoDSL xe2x80x9clifelinexe2x80x9d invocation is eliminated.
The LE is signalled during xe2x80x9clifelinexe2x80x9d invocation and repeal to indicate VoDSL xe2x80x9clifelinexe2x80x9d status.
The preferred features may be combined as appropriate, as would be apparent to a skilled person, and may be combined with any of the aspects of the invention.